First of all, a related art sleep mode operation will be described in detail with reference to FIG. 1. A mobile station (or mobile terminal or user equipment) may perform communication with a base station in a normal mode or an active mode, and, when there is no traffic to be transmitted or received to or from the base station, the mobile terminal may transmit a sleep request (hereinafter referred to as “AAI_SLP-REQ”) message to the base station, so as to request a shift in the operation mode to a sleep mode. As a response to the received sleep request message, the base station may transmit a sleep response (hereinafter referred to as “AAI_SLP-RSP”) message to the mobile station. Then, after receiving the transmitted sleep response message, the mobile station may shift its operation mode to the sleep mode by applying sleep parameters, such as a Sleep Cycle, listening window, and so on, which are included in the AAI_SLP-RSP message. Furthermore, by transmitting an unsolicited AAI_SLP-RSP message to the mobile station, the base station may shift the operation mode of the mobile station to the sleep mode.
FIG. 1 illustrates a related art sleep mode operation of a mobile station. As shown in FIG. 1, after shifting its operation mode from a normal mode to a sleep mode, the mobile station may operate in the sleep mode by applying an initial sleep cycle. After shifting to the sleep mode, the first sleep cycle include only a sleep window.
After the first sleep cycle, the mobile station activates the sleep mode by applying a sleep cycle, which includes a listening window and a sleep window, starting from the second sleep cycle. When the mobile station receives a traffic indication (hereinafter referred to as “TRF-IND”) message, which includes a negative indication, during the listening window, the mobile station determines that there is no traffic being transmitted via uplink. And, accordingly, the mobile station doubles the current sleep cycle. Once the doubled sleep cycle is completed, when the mobile station receives a TRF-IND message, which includes a positive indication, during the listening window of the next sleep cycle, the mobile station may reset the current sleep cycle to the initial sleep cycle.
Hereinafter, a method performed by the mobile station for updating information of an S-SFH SP IE (secondary super frame header subpacket information element) will be described in detail.
The mobile station receives a P-SFH IE (primary super frame header information element) and verifies an S-SFH change count field. Then, each time the S-SFH IE information is updated, the base station increments the value of the S-SFH change count field by 1.
When the mobile station verifies that the S-SFH change count value is different from the value assigned to the corresponding mobile station, the mobile station determines that the S-SFH SP IE has been changed. And, then, the mobile station verifies an S-SFH SP change bitmap of the P-SFH IE so as to determine which S-SFH SP has been updated.
Subsequently, the mobile station verifies S-SFH Scheduling information from the P-SFH IE, so as to determine which S-SFH SP IE is being transmitted from the current super frame. When an S-SFH SP IE, which is to be updated in the current SFH, is transmitted, the mobile station verifies and updates the corresponding S-SFH SP IE. Alternatively, when an S-SFH SP IE, which is to be updated in the current SFH, is not transmitted, the mobile station receives and updates an S-SFH SP IE in a next cycle during which the S-SFH SP IE that is to be updated in the current SFH is transmitted.
Thereafter, the S-SFH application hold indicator indicates the system parameter included in which S-SFH is being applied to the current super frame. More specifically, when the S-SFH application hold indicator is 0, the mobile station applies a system parameter related to an S-SFH change count field value of the current super frame. And, when the S-SFH application hold indicator is 1, the mobile station applies a system parameter related to ((S-SFH change count field value of the current super frame-1)modulo 16.
Table 1 indicates a format of the P-SFH IE.
TABLE 1SyntaxSize (bit)NotesP-SFH IE format ( ) { LSB of superframe number4Part of superframe number S-SFH change count4Indicates the value of S-SFH change count associatedwith the S-SFH SPx IE(s) transmitted in this S-SFH change cycle S-SFH size extension20b00: SizeSPx,extension = 00b01: SizeSPx,extension = 80b10: SizeSPx,extension = 160b11: SizeSPx,extension = 24 Number of repetitions for S-SFH2Indicate the number of repetitions used for S-SFH (NRep,S-SFH)transmission.0b00: reserved0b01: 60b10: 30b11: 1 S-SFH scheduling information2Indicates which S-SFH SP IE is included in S-SFHat this superframe0b00: S-SFH SP1 IE0b01: S-SFH SP2 IE0b10: S-SFH SP3 IE0b11: no S-SFH S-SFH SP change bitmap3Indicates the change in the content of S-SFH SPxIE(s) between current SFH and previous SFH associatedwith the S-SFH change count.If bit#0 (LSB) = 1, change in 3-SFH SP1 IE. Otherwiseno change in SP1 IE.If bit#1 = 1, change in S-SFH SP2 IE. Otherwise nochange in SP2 IE.If bit#2 (MSB) = 1, change in S-SFH SP3 IE. Otherwiseno change in SP3 IE. S-SFH application hold indicator1Indicate the S-SFH change count value used todetermine the S-SFH SPx IE content to apply in thissuperframe:0b0: Use S-SFH SPx IE content associated with thecurrent S-SFH change count0b1: Use S-SFH SPx IE content associated with (thecurrent S-SFH change count − 1) modulo 16 Reserved3The reserved bits are for future extension.
Table 2 indicates a format of the S-SFH IE. The system parameter and system configuration information, which are included in the S-SFH, may be categorized as S-SFH subpacket IE1 (S-SFH SP IE1), S-SFH SP IE2, S-SFH SP IE3. Herein, each of the S-SFH SP IE1, S-SFH SP IE2, and S-SFH SP IE3 is transmitted at different times at different cycles. S-SFH SP IE1 includes information for network reentry. S-SFH SP IE2 includes information for initial network entry and network discovery. And, S-SFH SP IE3 includes the remaining essential information for network (re)entry.
TABLE 2SizeSyntax(bit)NotesS-SFH IE format ( ) { if (S-SFH Scheduling information == 0b00) {  S-SFH SP1 IE ( )SizeSP1Includes S-SFH SP1 IE in Table 832.The size of S-SFH SP1 IE dependson FFT size.For 2048 FFT,SizeSP1, default = 96For 1024 FFT,SizeSP1, default = 90For 512 FFT,SizeSP1, default = 84 } else if (S-SFH Scheduling information == 0b01) {  S-SFH SP2 IE ( )SizeSP2Includes S-SFH SP2 IE in Table 833.The size of S-SFH SP2 IE dependson FFT size.For 2048 FFT,SizeSP2, default = 96For 1024 FFT,SizeSP2, default = 90For 512 FFT,SizeSP2, default = 86 } else if (S-SFH Scheduling information == 0b10) {  S-SFH SP3 IE ( )SizeSP3Includes S-SFH SP3 IE in Table 834.SizeSP3, default = 77 }}
Accordingly, in order to perform smooth communication with the base station, the mobile station operating in the sleep mode should be provided with the most recent (or recently updated) system information, that is being transmitted through the SFH. However, the related art method is disadvantageous in that, when a frame through which the P-SCH is being transmitted exists in the sleep window of the mobile station, the mobile station cannot receive the P-SCH, which enables the mobile station to determine whether or not a change in the system information occurs.